Feedback occurs when the output of a system is redirected as an input as part of the causal chain that forms a loop or loop. The system can then be said to provide feedback into itself. The causal idea should be handled with caution when applied to the feedback system:
Simple causal reasoning about the feedback system is difficult because the first system affects the second and second systems affecting the first, leading to a circular argument. It makes excuses based on complex causes and effects, and it is necessary to analyze the system as a whole.
Video Feedback
Histori
Self-regulatory mechanisms have existed since antiquity, and the idea of ​​feedback began to enter economic theory in England in the 18th century, but at that time was not recognized as a universal abstraction and has no name.
The verb phrase "to feed back", in the sense back to the previous position in a mechanical process, was used in the US in the 1860s, and in 1909 Nobel laureate Karl Ferdinand Braun used the term "bait behind "as a noun to refer (unwanted) coupling between electronic circuit components.
At the end of 1912, researchers using early electronic amplifiers (audions) have found that deliberately combining parts of the output signal back into the input circuit will increase amplification (via regeneration), but will also cause audions to howl or sing. The act of feeding back the signal from output to input led to the use of the term "feedback" as a different word in 1920.
Over the years there have been some disagreements over the definition of the best feedback. According to Ashby (1956), mathematicians and theorists interested in the principles feedback mechanism prefer the definition of the circularity of action, which keeps the theory simple and consistent. For those who have more practical purposes, feedback should be a deliberate effect through some more tangible connections.
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- "[Practical experiment] objected to the definition of mathematician, indicating that this would force them to say that the feedback is present in an ordinary pendulum... between its position and momentum - a 'feedback' that" From a practical point of view , rather mystical. For this, the mathematician responds that if feedback is considered only when there is actual wire or nerve to represent it, then the theory becomes chaotic and irrelevant. "/Dd>
Focusing on use in management theory, Ramaprasad (1983) defines feedback generally as "... information about the gap between the actual level and reference levels of system parameters" used to "change the gap in some way." He stressed that the information itself is not a feedback unless it is translated into action.
Maps Feedback
Type
Positive and negative feedback
There are two types of feedback: positive feedback and negative feedback.
For example, negative feedback, the diagram may represent a cruise control system in a car, for example, that matches the target speed like a speed limit. The controlled system is the car; its inputs include the combined torque of the engine and from the change in the slope of the road (interference). The speed of the car (status) is measured by speedometer. The error signal is the speed departure measured by the speedometer of the target speed (set point). This measurable error is interpreted by the controller to adjust the accelerator, ordering the fuel flow to the engine (effector). The resulting changes in engine torque, feedback, combined with the torque provided by the class path changes to reduce errors in speed, minimize road noise.
The terms "positive" and "negative" were first applied to feedback before World War II. The idea of ​​positive feedback already existed in the 1920s with the introduction of regenerative circuits. Friis and Jensen (1924) describe regeneration in a set of electronic amplifiers as a case where positive feedback actions are different from negative feedback actions, which they call only in passing. The classical paper Harold Stephen Black in 1934 explains in advance the use of negative feedback on electronic amplifiers. According to Black:
- "Positive feedback increases amplifier amplification, negative feedback reduces it."
According to Mindell (2002) the confusion in terms emerged shortly after this:
- "... Friis and Jensen have made the same distinction Black used between 'positive feedback' and 'negative feedback', based not on the feedback sign itself but on its effect on the contrary Nyquist and Bode , when they construct the work of Black, it refers to negative feedback because with the inverse sign, Black has difficulty persuading others about the usefulness of his invention in part because confusion lies above the fundamentals of the definition. "
Even before the terms applied, James Clerk Maxwell has described several types of "movement components" associated with centrifugal governors used in steam engines, distinguishing between those causing continuous increases in oscillation disturbances or amplitudes, and they which leads to the same decrease .
Terminology
The terms positive and negative feedback are defined in different ways in different disciplines.
- the change of the gap between the reference and the actual values ​​of a parameter, based on whether the loop is widened (positive) or narrow (negative).
- the valence of the action or effect that changes the gap, based on whether it has happy (positive) or unhappy (negative) emotional connotations to the recipient or observer.
Both definitions can cause confusion, such as when incentives (rewards) are used to improve poor performance (narrowing the gap). Referring to definition 1, some authors use alternate terms, replacing positive/negative with self-strengthening/self-correction , strengthening/balancing , incremental/regenerative/degenerative or regenerative/regenerative or regenerative/reduction gains. And for definition 2, some authors suggest describing actions or effects as positive/negative reinforcement or punishment rather than feedback. But even in a single discipline, the example of feedback can be called positive or negative, depending on how the value is measured or referenced.
This confusion may arise because feedback can be used for the purposes of information or motivation, and often has both qualitative and quantitative component. As Connellan and Zemke (1993) point out:
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- " Quantitative feedback tells us how much and how much. Qualitative feedback tells us how good, bad or indifferent."
Negative and positive feedback limits
While simple systems can sometimes be described as one or the other type, many systems with feedback loops can not be easily defined as only positive or negative, and this is especially true when multiple loops are present.
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- "When only two parts are joined so that each affects the other, the feedback traits provide important and useful information about the overall traits, but when the parts rise to at least four, if each people affect the other three, then twenty circuits can be traced through them, and knowing the properties of all twenty circuits does not provide complete information about the system. "
Other feedback types
In general, feedback systems can have many feedback signals and feedback often contains a mixture of positive and negative feedbacks where positive and negative feedback can dominate at different frequencies or different points in the system state space.
The term bipolar feedback has been created to refer to biological systems in which positive and negative feedback systems can interact, the output of one influencing input from another, and vice versa.
Some systems with feedback can have very complex behaviors such as chaotic behavior in non-linear systems, while others have more predictable behaviors, such as those used to create and design digital systems.
Feedback is widely used in digital systems. For example, binary counters and similar devices use feedback where the current state and input are used to calculate the new state which is then fed back and fed back to the device to update it.
Apps
Dynamic system
By using the feedback properties, the behavior of the system can be changed to meet the needs of the application; the system can be made stable, responsive or held constant. This shows that dynamic systems with feedback experience adaptation to the edge of chaos.
Biology
In biological systems such as organisms, ecosystems, or biosphere, most parameters must remain controllable within a narrow range around a certain optimal level under certain environmental conditions. The deviation of the optimal values ​​of the controlled parameters can result from changes in the internal and external environment. Changes to some environmental conditions may also require changing the range to change for the system to function. The parameter values ​​to maintain are recorded by the receiving system and passed to the regulatory module through the information channel. An example of this is oscillation of insulin.
Biological systems contain many types of regulatory circuits, both positive and negative. As in other contexts, positive and negative does not imply that feedback causes either good or bad . Negative feedback is one that tends to slow down the process, whereas positive feedback tends to speed it up. Mirror neurons are part of the social feedback system, when the observed action is "mirrored" by the brain - just as the act itself does.
Feedback is also important for gene operation and gene-setting tissue. Repressors (see Lac Reploresor) and activator proteins were used to create genetic operons, identified by Francois Jacob and Jacques Monod in 1961 as a feedback loop . This feedback loop may be positive (as in the case of coupling between sugar molecules and proteins that import sugar into bacterial cells), or negative (as is often the case in metabolic consumption).
On a larger scale, feedback can have a stabilizing effect on the animal population even when strongly influenced by external changes, although time delays in feedback responses can lead to predator-prey cycles.
In zimology, feedback serves as a regulation of enzyme activity by the direct product (s) or downstream metabolite (s) in the metabolic pathway (see Allosteric regulation).
The hypothalamic-pituitary-adrenal axis is largely controlled by positive and negative feedback, much of which remains unknown.
In psychology, the body receives stimuli from the environment or internally that causes the release of hormones. The release of hormones can then cause more hormones to be released, causing positive feedback loops. This cycle is also found in certain behaviors. For example, the "shy circle" happens to people who are easily blushes. When they realize that they are flushed, they become more embarrassed, leading to further flushing, and so on.
Climatic science
The climate system is characterized by a strong positive and negative feedback loop between processes affecting atmospheric, marine, and soil conditions. A simple example is a positive ice-albedo feedback loop where melting snow shows darker soil (low albedo), which in turn absorbs heat and causes more snow to melt.
Control theory
Feedback is widely used in control theory, using a variety of methods including state space (control), full-state feedback (also known as polar placement), and so on. Note that in the context of control theory, "feedback" is traditionally assumed to define "negative feedback".
The most common general-purpose controller using a loop-control feedback mechanism is a proportional-integral-derivative (PID) controller. Heuristically, the PID controller's provision can be interpreted as time-dependent: the proportional term depends on the error present , the integral term on the accumulated error the past, and the derivative term is a prediction error future , based on the current rate of change.
Mechanical engineering
In ancient times, the floating valve was used to regulate the flow of water in Greek and Roman water watches; Similar floating valves are used to adjust the fuel in the carburetor and are also used to regulate the water level of the tank in the flush toilets.
Dutch inventor Cornelius Drebbel (1572-1633) built a thermostat (c1620) to control the temperature of chicken incubators and chemical furnaces. In 1745, the windmill was repaired by the blacksmith Edmund Lee, who added an owl to keep the windmill face pointing to the wind. In 1787, Thomas Mead set the speed of the windmill round by using a centrifugal pendulum to adjust the distance between the tombstones and the runner (ie, to match the load).
The use of the centrifugal governor by James Watt in 1788 to regulate the speed of his steam engine was one of the factors that led to the Industrial Revolution. Steam engines also use valve buoys and pressure relief valves as a mechanical setting device. Watt's governor's mathematical analysis was performed by James Clerk Maxwell in 1868.
The Great Eastern was one of the largest steamers of its time and used steam-powered steering with a feedback mechanism designed in 1866 by John McFarlane Gray. Joseph Farcot coined the word
Internal combustion engines at the end of the 20th century used mechanical feedback mechanisms such as the progress of vacuum time but mechanical feedback was replaced by an electronic engine management system after a small, powerful and powerful single chip microcontroller became affordable.
Electronic engineering
The use of feedback is widespread in the design of electronic amplifiers, oscillators, and elements of stateful logic circuits such as flip-flops and counters. Electronic feedback systems are also very commonly used to control physical, thermal and other physical processes.
If the signal is reversed on the loop of the control loop, the system is said to have negative feedback ; if not, feedback is positive . Negative feedback is often deliberately introduced to improve the stability and accuracy of a system by correcting or reducing the effects of unwanted changes. This scheme may fail if input changes faster than the system can respond. When this happens, delay arrival of the correction signal may result in overcorrection, causing the output to oscillate or "hunt". Although often an undesirable consequence of system behavior, this effect is used deliberately in an electronic oscillator.
Harry Nyquist donated the Nyquist plot to assess the stability of the feedback system. An easier, but less common, assessment is based on profit margins and phase margins using the Bode plot (donated by Hendrik Bode). The design to ensure stability often involves frequency compensation, one of the compensation methods that divides the poles.
An electronic feedback loop is used to control the output of an electronic device, such as an amplifier. A feedback loop is created when all or some parts of the output are fed back to the input. The device is said to operate open loop if no output feedback is used and closed loop if feedback is used.
When two or more amplifiers cross each other using positive feedback, complex behavior can be made. multivibrators are widely used and include:
- astable circuit, which acts as an oscillator
- a monostable circuit, which can be pushed to a state, and will return to a stable state after some time
- bistable circuit, which has two stable states that the circuit can be routed between
Negative feedback
Negative feedback occurs when the feedback output signal has a relative phase of 180 ° to the input signal (inverted). This situation is sometimes referred to as out of phase , but the term is also used to indicate other phase separation, as in "90 Â ° phase". Negative feedback can be used to correct output errors or to reduce system sensitivity to undesirable fluctuations. In the feedback amplifier, this correction is generally for the reduction of wave distortion or to establish the specified gain level. The common expression for negative feedback amplifier reinforcement is the asymptotic gain model.
Positive feedback
Positive feedback occurs when the feedback signal is in phase with the input signal. Under certain reinforcement conditions, positive feedback amplifies the input signal to the point at which the device's output oscillates between its maximum and minimum possibilities. Positive feedback can also introduce hysteresis into the circuit. This may cause the circuit to ignore small signals and only respond to large signals. Sometimes it is used to remove sound from digital signals. In certain circumstances, positive feedback can cause the device to loosen, that is, to achieve a condition in which output is locked to a maximum or minimum state. This fact is very much used in digital electronics to create bistable circuits for storing volatile information.
The loud exclamations that sometimes occur in audio systems, PA systems, and rock music are known as audio feedback. If the microphone is in front of the connected loudspeaker, it is heard that the microphone picks up out of the speakers, and is picked up by the microphone and reinforced. If loop gain is enough, howling or screeching at the maximum strength of the amplifier is possible.
Oscillator
An electronic oscillator is an electronic circuit that produces periodically oscillating electronic signals, often sine or square wave. The oscillator converts the direct current (DC) from the power supply into an alternating current signal. They are widely used in many electronic devices. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters, clock signals that regulate computers and quartz clocks, and sounds generated by electronic beepers and video games.
The oscillator is often characterized by the frequency of its output signal:
- A low frequency oscillator (LFO) is an electronic oscillator that generates the frequency below? 20 Hz. The term is commonly used in the field of audio synthesizers, to distinguish it from an audio frequency oscillator.
- The audio oscillator produces a frequency in the audio range, about 16 Hz to 20 kHz.
- An RF oscillator generates a signal in the radio frequency range (RF) of about 100 kHz to 100 GHz.
Oscillators designed to produce high-powered AC output from a DC supply are usually called inverters.
There are two main types of electronic oscillators: linear or harmonic oscillators and nonlinear or relaxation oscillators.
Hooks and flip-flops
The hook or flip-flop is a circuit that has two stable states and can be used to store state information. They are usually built using feedback that traverses between two arm circuits, to provide circuits with states. Circuits can be made to change the state with the signal applied to one or more control inputs and will have one or two outputs. This is the basic storage element in sequential logic. Hooks and flip-flops are basic building blocks of digital electronic systems used in computers, communications, and many other types of systems.
Hooks and flip-flops are used as data storage elements. Such data storage can be used for storage of state , and such circuits are described as sequential logic. When used in a state-limited machine, the output and subsequent state depend not only on the current input, but also on its current status (and hence, the previous input). It can also be used to count pulses, and to synchronize input signals that vary in time to some time reference signals.
Flip-flops can be either simple (transparent or blurry) or clocked (synchronous or edge triggered). Although the term flip-flop has historically been referred to generally for both simple circuits and clocks, in modern usage it is common to order the term "flip-flop" exclusively to discuss the clock circuit; simple ones are usually called hooks .
Using this terminology, the latch is level-sensitive, while the flip-flop is tip-sensitive. That is, when a latch is activated, it becomes transparent, while the flip flop output only changes in one type (positive or negative appearance) from the clock edge.
Software
Feedback loops provide a common mechanism for controlling the running, maintenance, and evolution of software and computing systems. Loop feedback is an important model in adaptive software engineering, as they define interaction behavior among control elements during the adaptation process, to ensure system properties at run-time. Feedback and the foundations of control theory have been successfully applied to computing systems. In particular, they have been applied to product development such as IBM Universal Database server and IBM Tivoli. From a software, autonomous (MAPE, monitor analyzing implementation plan) loop perspective put forward by IBM researchers is another valuable contribution to feedback loop applications for controlling dynamic properties and design and evolution of autonomous software systems.
Design user interface
Feedback is also a useful design principle for designing user interfaces.
Video feedback
Video feedback is a video equivalent of acoustic feedback. This involves a loop between the video camera's input and video output, for example, a television screen or monitor. Directing the camera to the screen produces complex video images based on feedback.
Social science
Economy and finance
The stock market is an example of a system susceptible to oscillating "hunting", governed by positive and negative feedback resulting from cognitive and emotional factors among market participants. As an example:
- As stocks rise (bull market), higher rising confidence is likely to incentivize investors to buy (positive feedback - strengthen gains, see also stock market bubble and momentum investment); but the rise in stock prices, and the knowledge that there should be a peak after the market falls, ends inhibiting the buyer (negative feedback - stabilizing the increase).
- Once the market begins to fall regularly (bear market), some investors may expect to lose further days and refrain from buying (positive feedback - strengthening fallout), but others may buy as stocks become more and cheaper ( negative feedback - stabilize the fall, see also contrarian investment).
George Soros uses the word reflexivity to illustrate feedback on financial markets and develop investment theory based on this principle.
The model of economic equilibrium of conventional supply and demand only supports negative linear feedback and is strongly criticized by Paul Ormerod in his book The Death of Economics, which, in turn, is criticized by traditional economists. This book is part of a change of perspective when economists begin to recognize that chaos theory is applied to nonlinear feedback systems including financial markets.
See also
References
Further reading
- Katie Salen and Eric Zimmerman. Rules of Play . MIT Press. 2004. ISBNÃ, 0-262-24045-9. Chapter 18: Game as a Cybernetic System.
- Korotayev A., Malkov A., Khaltourina D. Introduction to Social Macrodynamics: The Secular Cycle and Millennium Trends. Moscow: URSS, 2006. ISBNÃ, 5-484-00559-0
- Dijk, E., Cremer, D.D., Mulder, L.B., and Stouten, J. "How Do We React to Feedback in a Social Dilemma?" In Biel, Eek, Garling & amp; Gustafsson, (eds.), New Problems and Paradigms in Research on Social Dilemma , New York: Springer, 2008.
External links
- Media related to Feedback on Wikimedia Commons
Source of the article : Wikipedia
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